The enzyme glucokinase (GK), which is mainly found in pancreatic β-cells and liver parenchymal cells, catalyzes the conversion of glucose to glucose-6-phosphate, which is the first step in the metabolism of glucose. Glucokinase is also a rate-controlling enzyme for glucose metabolism in pancreatic β-cells and liver parenchymal cells, which play an important role in whole-body glucose homeostasis.
Liag, Y. et al. (Biochem. J., 309:167-173 (1995)) report the finding that Type II (maturity-onset) diabetes of the young (MODY-2) is caused by loss of function mutations in the glucokinase gene, which suggests that glucokinase also functions as a glucose sensor in humans. Thus, compounds that activate glucokinase and thus increase the sensitivity of the glucokinase sensor system and thereby cause increase in insulin secretion will be useful in the treatment of hyperglycemia and Type II diabetes.
Glucokinase activators have been demonstrated to be effective in enhancing: 1) the effect of glucose on insulin release from isolated rat and human pancreatic islets, and 2) the glucose induction of pancreatic islet glucokinase in isolated cultured rat islets (e.g., Matschinsky, F. M. et al., Diabetes, 55:1 (2006), and (Matschinsky, F. M. et al., eds., Glucokinase and Glycemic Disease, from Basics to Novel Therapeutics, Karger, publ., Ch. 6, pp. 360-378 (2004)). In diabetic animal model studies, glucokinase activators have been demonstrated to stimulate insulin release, enhance glycogen synthesis and reduce hepatic glucose production in pancreatic clamp studies. Importantly, glucokinase activators have been demonstrated to dose-dependently lower blood glucose levels in different standard animal models of type 2 diabetes, such as the ob/ob mouse, db/db mouse and Zucker fa/fa rat in acute single-dose studies and also effectively improved the glucose excursion in both normal C57/BL6J and ob/ob mice in oral glucose tolerance tests (e.g., in Matschinsky, F. M. et al., eds., Glucokinase and Glycemic Disease, from Basics to Novel Therapeutics, Karger, publ., Ch. 6, pp. 360-378 (2004); as well as Fyfe, M. C. et al., Diabetologia, 50:1277 (2007)).
Glucokinase activators have also demonstrated antidiabetic efficacy in chronic animal models of type II diabetes. For instance, in a 9-day study in ob/ob mice, a glucokinase activator improved the overall glucose profile while showing comparable antihyperglycemic effects in oral glucose tolerance tests at the beginning and end of the study (Fyfe, M. C. et al., Diabetologia, 50:1277 (2007)). In another instance, in a chronic 40-week study, a glucokinase activator prevented the development of hyperglycemia in diet-induced obese mice which were glucose intolerant. The diet-induced obese mice treated with a glucokinase activator showed marked improvement in the glucose excursion in an oral glucose tolerance test at the end of the study relative to the control group Matschinsky, F. M. et al., eds., Glucokinase and Glycemic Disease, from Basics to Novel Therapeutics, Karger, publ., Ch. 6, pp. 360-378 (2004)).